package com.utils;

import cn.hutool.core.codec.Base64;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.Key;
import java.security.Security;
import java.util.Arrays;

public class WeixinUtil {

        public static void main(String[] args) {
            String result = WeixinUtil.decryptData(
                    "xCv/yD0GQ7+t1cx/IuGaAzAGZ931UOn822KlhAxMMBqcNKGefgsRytVl9ysaNn+hFPqtb4qphguIHvVDRV7kmwZccGxli5J41lyI1fjemRuDvyng//XTZzDno3eCp+9q9eGrh3OVoL5GipRnNqRVtABJ7ummOAcY9tWoRPM2ee2YEX/OT+OAaoylR2kyXFZk7VsN4iB6+23HmAyQtnwzIobqSkhNNvQRDyYLrOB8q+D7MCfaYbXQpA4wbmHxSLnB3d6tqL/w0YlmUzMbPjmGbZD3frW4yAsaJ0oMLtHJRR1g/SlPgCtGlhhoSPXqHrOg8dRtRcwO8ileuYGykKm72ZWxCmRIfDjAFUetocQuLlaKp8ikIfhr3zbFjuC0G87dBHZTs+YmVAGDOIy1xP7FbL46bxcSdRPdfW5eOrO/B3zjXafu65gzY4FgUY45QoEO+HPEZNzqjNqRPyMHX+gcERICyVqArmh2g899Rro+ubU=",
                    "FvEs/ZiJQBJr5nrs2LX1AA==",
                    "fxSKjXsRur6jpzZMM6PM7w=="
            );
            System.out.println("result = " + result);
        }

    /**
     * 解密用户信息中加密部分
     * @param encryptDataB64  加密数据
     * @param sessionKeyB64   解密key
     * @param ivB64           解密iv
     * @return
     */
        public static String decryptData(String encryptDataB64, String sessionKeyB64, String ivB64) {
            return new String(
                    decryptOfDiyIV(
                            Base64.decode(encryptDataB64),
                            Base64.decode(sessionKeyB64),
                            Base64.decode(ivB64)
                    )
            );
        }

        private static final String KEY_ALGORITHM = "AES";
        private static final String ALGORITHM_STR = "AES/CBC/PKCS7Padding";
        private static Key key;
        private static Cipher cipher;

        private static void init(byte[] keyBytes) {
            // 如果密钥不足16位，那么就补足.  这个if 中的内容很重要
            int base = 16;
            if (keyBytes.length % base != 0) {
                int groups = keyBytes.length / base + (keyBytes.length % base != 0 ? 1 : 0);
                byte[] temp = new byte[groups * base];
                Arrays.fill(temp, (byte) 0);
                System.arraycopy(keyBytes, 0, temp, 0, keyBytes.length);
                keyBytes = temp;
            }
            // 初始化
            //Security.addProvider(new BouncyCastleProvider());
            // 转化成JAVA的密钥格式
            key = new SecretKeySpec(keyBytes, KEY_ALGORITHM);
            try {
                // 初始化cipher
                cipher = Cipher.getInstance(ALGORITHM_STR, "BC");
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        /**
         * 解密方法
         *
         * @param encryptedData 要解密的字符串
         * @param keyBytes      解密密钥
         * @param ivs           自定义对称解密算法初始向量 iv
         * @return 解密后的字节数组
         */
        private static byte[] decryptOfDiyIV(byte[] encryptedData, byte[] keyBytes, byte[] ivs) {
            byte[] encryptedText = null;
            init(keyBytes);
            try {
                cipher.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec(ivs));
                encryptedText = cipher.doFinal(encryptedData);
            } catch (Exception e) {
                e.printStackTrace();
            }
            return encryptedText;
        }

}
